Geographic location referencing system and method

ABSTRACT

A method and apparatus for defining grid and proprietary addresses of selected locations within a geographical area is described, characterized in that the grid addresses are defined in relation to a grid and can be easily converted to global coordinates defined in relation to a known global referencing system, and the proprietary addresses are unique to the geographical area.

This is a continuation of application Ser. No. 08/701,586 filed Aug. 22,1996, which issued Nov. 17, 1998 as U.S. Pat. No. 5,839,088.

BACKGROUND OF THE INVENTION

The field of this invention is geographic location referencing systems.

A geographic location system has an addressing scheme that allows alocation to be uniquely addressed. Several systems are well known andcurrently in use, such as geodetic latitude and longitude, UniversalTransverse Mercator (UTM), Military Grid Reference System (MGRS), WorldGeographic Reference System (GEOREF), Maidenhead, Trimble Grid, TrimbleAtlas, and Thomas Brothers Detail. These known systems can generally bedivided into two categories: global and local. The global systems, suchas geodetic latitude and longitude, UTM, MGRS, GEOREF, Maidenhead, andTrimble Grid, use a scheme that subdivides the globe into areas ofincreasing resolution, until a particular location is properlyidentified. Thus each location address is referenced to the globalsystem, allowing for the easy comparison of mwo location addresses.However, the addresses tend to be complicated, cumbersome, and unrelatedto the real world, increasing the complexity of these systems.

The local systems, such as Thomas Brothers paper mapping systems,provide a technique that assigns location addresses based on associationwith a geographic region or physical map pages, with every locationidentified with only one region. This type of local system is easier touse for local location information in connection with a physical map,but is difficult to use win respect to a more global or electronicsystems, as there is no simple way to convert a local address into aglobal address, and the local address is not recognized in the globalsystems.

Location technology has been significantly impacted by the wideavailability of Global Positioning Systems (GPS), which axe operated bythe United States Department of Defense to provide worldwide navigation,position location, and precision timing services. GPS comprises a globalnetwork of satellites that interact with a controller coupled to a GPSreceiver, allowing the controller to precisely determine its location.This location is typically output from the GPS receiver as latitude andlongitude numbers, which are cumbersome for users to understand and use.A GPS receiver is sometimes coupled with additional capability thatallows the raw latitude/longitude numbers to be converted into a moreuseful and usable format. See, e.g., Sprague et al., U.S. Pat. No.5,422,814; Inoue, U.S. Pat. No. 5,289,195; and Yamashita, U.S. Pat. No.5,471.392. However, even with these enhancements, a problem with thesesystems is that they are still difficult to use by persons who areunskilled in the use of location referencing systems. Another problem isthat these systems are unwieldy because they still retain their globalcharacter. Thus, what is needed is a referencing system that can be usedwith a minimum amount of reading, scrolling, and searching, and with alimited number of keystrokes for data entry. Also needed is auser-friendly, truly local addressing system that is easily convertibleto a known global system for wide-range concerns.

SUMMARY OF THE INVENTION

The present invention relates to creating and using a locationreferencing address method associated with an established geographicinformation system. The location referencing address method has anarbitrary local referencing system that retains a known relationshipwith a global referencing system.

In a first, separate aspect of the present invention, a universallocation address is defined by subdividing a geographic location intoseveral independent districts, each with a name and a reference point.The reference point has a known locational address within a globalreferencing system. A coordinate system is placed on the districtrelative to the reference point, yielding a position indicator forlocations within the district. Combining the district name and theposition indicator defines the local location.

In a second, separate aspect of the invention, the foregoing aspect maybe further enhanced by the creation of proprietary locational addresses.A proprietary address is a name, which will be unique within thedistrict, that distinctly identifies a location with the district. Aproprietary address is created by selecting a name, capturing positionalinformation about the location associated with the name, checking thatthe name is unique in the district and storing the name with itsassociated locational information and feature data. Once stored, thename and the associated information may be selectively disseminated tousers of locational systems.

In a third separate aspect of the invention, a locational system firstaccepts regional or positional information to determine a generallocation address, including a district name. The locational system thenaccepts specific addresses, each having less than a complete locationaladdress. The locational system creates a complete locational address bycombining the known general positional information with the abbreviatedspecific locational address to determine the precise and completelocational address, generally by prefixing the known general positionalinformation to the specific locational address.

In a fourth separate aspect of the invention, a navigational systemincorporating the foregoing aspects is defined.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 shows two overlapping districts, each with a reference point anda grid system.

FIG. 2 shows a single cell of FIG. 1 with hierarchical gridding toincrease the addressing resolution.

FIG. 3 is a functional diagram of a preferred embodiment of theinvention.

FIG. 4 shows how proprietary locational names are compiled anddistributed.

FIG. 5 is a diagram of a navigational system incorporating one or moreaspects of the subject invention.

FIGS. 6 and 7 show the use of PLAs and ULAs in a specific geographicalcontext.

FIGS. 8a-8b, 9, 10a-10c, 11 are examples of specific files used in oneimplementation of the subject invention.

FIGS. 12a-12c are examples of screen outputs used in one implementationof the subject invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention allows a point ofinterest (POI) within an arbitrary geographic area to be uniquelyidentified with a locational address, and the locational address to berelated to other known global referencing systems. The locationaladdress may take two forms: first as a universal locational address(ULA); or second, as a proprietary locational address (PLA). Each ofthese forms is discussed below.

Every location in a geographic area will have at least one ULA. Todetermine the ULA of a point, a geographic area is divided into severaldistricts. The districts may be of differing size and shape, and maycontain a particular identifying feature. For example, the geographicarea of the United States may be subdivided into numerous districts,which may be strategically located, sized, and named with reference tocities or other geographic or political features in order to associatethe districts with such features. Advantageously, such districts arechosen relative to cities and it is therefore convenient to name eachdistrict according to the city about which the district is located. Infact, each city may have a reference point, allowing local locations tobe addressed relative to the local city. Sparsely populated areas mayhave larger districts. and densely populated areas may have smallerdistricts. The districts may also be quasi-rectangular, followinglatitude and longitude lines. In more densely populated areas, it ispossible that a particular location will be within the boundaries of twoor more districts. In addition, user-defined districts, referencepoints, and grid sizes are possible. For example, a search and rescueoperation may establish a reference point and grid size convenient for aparticular search area, or a group of hikers may choose a referencepoint and grid size appropriate for a particular outing.

After the districts have been selected and named a reference point ischosen for each district, and a grid system placed relative to thereference point. Advantageously, the grid system is referenced north.Referring to FIG. 1, a first district 1 and a second district 3 aredefined relative to major cities 4 and 6 respectively. In this example,major city 4 in the first district 1 will be named CITYONE and the majorcity 6 in the second district 3 will be named CITYTWO. For convenience,the first district 1 will be named CTY1, referring to the major citywithin that district's borders, and the second district will be namedCTY2, referring to the major city within that district's borders.Reference point 5 is selected as the reference point for CTY1, andreference point 7 is selected as the reference point for CTY2. Thereference point will not necessarily be located proximate to the featureused as the name for the district. Each reference point 5 and 7 has aknown address within a global referencing system such as World GeodeticSystems (WGS). Association with a global system offers at least threeimportant functions: first, local addresses may be easily converted toglobal addresses and vice-versa; second, inter-district relationshipsare established; and third, easy integration with known navigationalsystems is provided. Thus, an easy to use district-level addressingsystem retains the advantages of a global system without attachingcomplexity.

As can be seen in FIG. 1, the grid system about each reference point 5and 7 creates cells 9 in each district. Each of these cells 9 isidentified with a cell code, which advantageously is a two characternumber. For example, a target POI location 19, which is in cell 11, cannow be identified by referring to its district and cell code, e.g.,CTY2-11. Of course, such a reference lacks the resolution to identify aparticular feature, such as a house, but may be enough resolution tolocate a lake or park. The issue of increased resolution is discussedbelow.

Also, it is likely that there will be an overlap area 13 that is formedat the intersection of districts. Within this overlap area 13, any POIcan be identified by reference to any district within which it islocated. Thus, a target location 8 in the overlap area 13 can beidentified by either association with the CTY1 or CTY2 districts, or anyother district within which it is located. In the preferred embodiment alocational system can provide a locational address relative to anyreference point or district by simply toggling between reference points.

As discussed above, a district name and cell code may not givesufficient resolution to locate specific locations. To increaseresolution, a hierarchical grid is applied to each cell 9 of FIG. 1. Forexample, cell 11 is shown in FIG. 2 with a sub-grid applied, producingsub-cells 15. Each of these sub-cells can be identified with a sub-gridcode. Moreover, the sub-cells can be further subdivided to increaseresolution. Here, sub-cell 17 is further subdivided. As can be seen inthe figure, the target location 19 is within the sub-sub cell 18. Thus,to more definitively identify the target location 19, a ULA is formedfrom the highest resolution subcell defined and each of its parentcells. The locational address is formed by appending to the districtname each sub-cell code in hierarchical progression, moving from lowerresolution to more resolution. In the example here, the target location19 would have a locational address of CTY2-11-17-18. Based on the sizeof the district, if this does not give the necessary resolution toproperly locate the target location 19, then additional levels ofgridding hierarchy can be added. Although, in this example, each cellwas randomly named with a unique numerical code, it should beappreciated that a consistent Cartesian coordinate system can also beused, with each cell defined by an (X, Y) coordinate pair. Those skilledin the art will recognize several other alternative ways to define agrid system.

Advantageously, a city will be named with a specific abbreviated namefor purposes of navigating to and around that city. That abbreviatedname may also serve as the name of the defined district located aboutthat city. Depending on the size of the city and various geographic,political, and other features relating to the city or region, thedistrict for that particular city will be pre-defined with a particulargrid size, although the system may allow altering the grid size forparticular purposes. If, in the preceding example, the defined grid sizefor CTY2 is approximately 30 by 30 nautical miles. identifying twohierarchial grids produces a resolution of about 500 meters. which issufficient for locating structures in open areas or large targets suchas lakes or parks. By adding a third and fourth hierarchical grid, aresolution of about 5 meters is achieved, and by adding a fifthhierarchical grid, a resolution of about 0.5 meters is achieved. Byadjusting the number of grids, then, the resolution of the resultinglocational address is changed to meet the requirements of the particulararea or user. Advantageously, each level of the hierarchial address isseparated by a decimal point. Thus an address may appear as "DISTRICT.12.34.56.79". Those skilled in the art will recognize severalalternatives to this approach

The second way a point of interest may be designated in the subjectinvention is with a proprietary locational address (PLA). Referring toFIG. 4, the first step in using a PLA is to identify the feature andselect a name 51. A PLA is a name chosen to identify a physicalstructure or location. The name can be chosen by the operator of alocational service, as in the case of naming national monuments, or thename can be chosen by individual or corporate users of the locationalservice. Individuals may even want to identify their homes using theirown names. Thus, a Ms. Mary Smith may name her house MARY.SMITH.HOUSE,for example. Thus, when Ms. Smith wants to direct someone using alocational service to her house, she identifies her location usingMARY.SMITH.HOUSE, rather than a street address or other locationalreferencing system. A corporation, too, may desire to allow customers tolocate it using a common name rather than a less personal addressingsystem. For example, a nationwide enterprise such as MacDonalds™ withmany locations may choose a PLA that is associated with its tradename orproduct or otherwise allows users to easily remember and associate theestablishment's PLA. Abbreviations are usefull as it keeps user input toa minimum, increasing safety, reliability, and convenience. Since thenation-wide enterprise may have many locations in a single metropolitanareas, each may be identified by appending to the enterprise's PLA aunique identifier to identify specific branch offices or affiliates.Wildcard searching is also provided, allowing several locations of theknown nation-wide enterprise to be found for a particular geographicarea.

The capture of positional information for a certain name will now bedescribed. Referring to FIG. 4. as indicated by identifying numeral 55,positional information could be entered manually, by, for example,inputting the ULA or coordinates of the location from a known mappingsystem. Alternatively, as indicated by identifying numeral 57, thepositional information may be read electronically using a system such asthe GPS. Referring again to FIG. 4, the name 51 and positionalinformation 53 are associated. The district in which the location isidentified is determined by comparing the positional information 53 tostored district locational information 54. Once the district isidentified, the name is checked against other reserved names in thedistrict to assure the selected name is unique. If the name is unique,it is placed in a district data file 63. As can be seen from thediscussion above, uniqueness of the name need only be checked at thedistrict level. Consequently, the same name can be present in differentdistricts. The name must be unique at the district level as the districtname usually becomes part of the PLA. For example, the nation-wideenterprise location in district CTY1 could have a full PLA ofCTY1-TRADENAME. If the owner of a name desires to more widely reserve aname, each district will be checked individually.

Once a PLA is approved for an individual, corporation, or other entity,the PLA may be placed in promotional material such as advertisements,coupons, billboards, or other means of communication. By providing a PLAthat describes a feature, a particular location may be quicklyidentified and readily found.

Once cleared for conflicts, the name, positional information, and anyother useful information are stored in a central repository location.This storage may be sortable and selectively downloadable by users oflocational systems. For example, the central repository may beaccessible via the Internet. In such a case, a user 75 would make arequest for information 71 concerning future travel, such as the ULAs orPLAs of specific desired waypoints of a trip. The information in thecentral repository 65 is selected and sorted, and the travel data 73 isreceived by the user, creating a travel profile. To ease the dataselection process. the central repository may store preferences for theuser. After receiving the travel profile, the user places the traveldata 73 into a navigational unit 77, augmenting information 79 alreadylocally present in the navigational unit 77. The user 75 may then usethe travel data 73, including PLAs and ULAs, to assist in navigating.

An aspect of the subject invention is the use of ULAs and PLAs in knownnavigational systems. The use of a ULA by such a system with a minimumamount of information input by a user will now be disclosed. Referringto FIG. 3, district file 31 is maintained correlating district names andlocational information relating to those districts. Regional information33, that may be manually entered (as indicated by reference numeral 21)by a user, may also be maintained. This regional information 33 is usedby the system to reduce the amount of information a user must enter toidentify a particular location. The regional information may, forexample, be a map code or distinct name identifying the general areacovered by the map. Alternatively, it may be the name of a districthaving a pre-defined grid. After the map code or district name isinputted as regional information, the system now assumes that any futureuser inputs are within the geographical area defined by the regionalinformation, thus reducing the complexity of inputting future addressesreferenced on that map. Also, positional information 35 of a currentlocation may be input manually (reference numeral 23) or electronically(reference numeral 25) for the same purpose. By knowing the presentlocation, the system may assume that any subsequent address input by theuser is within the same geographical area as the present location.Again, the purpose and effect is to reduce the complexity of inputtinglocational addresses.

The user may also electronically (reference numeral 29), or manually(reference numeral 27) input a specific address 37 to the system. Bycomparing the regional information 33 and positional information 35 ofthe current location with the stored district information 31, a generaladdress can be formed. This general address will contain the districtname plus any cell and sub-cell codes that are more general than themost general code in the specific address. The resolution detector 43attempts to determine how much resolution is represented by the specificaddress 37 input by the user, and in conjunction with the comparison 41function, creates a general address 45 with the correct level ofresolution. Again, it is assumed that any subsequent addresses input bythe user are within the same geographical area defined by this generaladdress.

Once the resolution of the specific information 37 is determined, thespecific information 37 is passed on to become a specific address 47.This specific address 47 is appended to the general address 45 formedabove to form the final locational address 49. The locational address 49is then used by the navigational system to assist in navigation.Additionally, an emergency mode may be provided in which a presentlocation is automatically referenced to any reasonably close PLA orother known location.

A relationship with World Geodetic System 1984 (WGS-84), allowinglocational addresses to be converted to other global addressing systems,is also provided. A further description of the district grid is neededto understand this relationship. Each district has a reference point,with the reference point being the approximate center of the city usedin naming the district A grid is placed in relation to the referencepoint such that the origin of the grid is aligned with the nearestintersection of latitude and longitude lines corresponding to thelargest grid resolution in the district Since the reference point has aknown WGS-84 address, by knowing the origin offset, the districtrotation, and the district scale, every ULA can be translated into aWGS-84 address, and from there into nearly all locational referencesystems. Conversely, every WGS-84 address may be translated into one ormore ULAs. The translation is simplified in the subject invention as thedistrict grid system is generally aligned to the WGS-84latitude/longitude grid.

With reference to FIG. 5, such a system comprises a GPS receiver 100, aninput device 101 such as a keypad or the like, a processor 102, astorage device 103 such as RAM or ROM, and an output device 106 such asa display. The GPS receiver 100, input device 101, storage device 103,and output device 106 are all coupled to the processor 102 as shown. Anapplication program 104 executes in the processor to perform varioustasks. Optionally, a look-up-table (hereinafter "LUT") 105 is providedin the storage device 103.

The application program in a conventional navigational apparatustypically interfaces with and directs the aforementioned elements toperform the following tasks:

1. Displays the latitude and longitude (hereinafter "lat/lon") of theunit--First, the GPS receiver receives signals from the GPS satelliteconstellation, and calculates the location of the unit (in terms oflat/lon) using these signals. The lat/lon coordinates of the unit arethen displayed on the output device 106.

2. Displays velocity and bearing--if the unit is moving, the processordetermines the location of this unit at selected time intervals, andbased thereon, determines velocity and bearing. Once determined, thisinformation is displayed on the output device 106.

3. Allows for the selection of waypoints--In one approach, a user inputswaypoints through input device 101 in terms of lat/lon coordinates. Inanother approach, common in the aviation community, a look-up-table orthe like, identified with numeral 105 in FIG. 5, is provided,correlating predetermined waypoints with lat/lon coordinates. Acapability for searching through the database and selecting particularwaypoints is also provided in this approach.

4. Displays distance and bearing from selected waypoints--once thewaypoints have been determined, the distance (assuming straight line)and bearing from these waypoints is determined and displayed.

Additional components of the system which are added by the subjectinvention include context buffer 108; front-end interface (hereinafter"FEI") 107; PLA database 110; and a database(s) 109 of grid definitions.

A critical function of the front-end-interface is to convert ULAs andPLAs into tat/lon coordinates. Consequently, a user can input waypointsin terms of ULAs or PLAs, and the FEI will convert the same to lat/loncoordinates for use by the unit in determining a directional and/ordistance indicator (such as distance and bearing) from the waypoints.Additionally, positional information defined in terms of lat/loncoordinates can be displayed in terms of one or more ULAs of the subjectinvention. The FEI also includes various searching capabilities to allowa user to search through the PLA database 110 for particular waypointsor waypoints with particular characteristics.

The function of the context buffer 108 is to define the current districtand grid in which grid addresses are assumed to be defined.

The grid definition file(s) 109 specifies all the grids which have beendefined to date. For each grid, all the parameters necessary to definethe gird are stored. Such information includes the lat/lon coordinatesof the reference point of the grid, the dimensions of the grid, and therotation and scaling of the grid cells. Thus, all the information neededto convert between a grid address within the grid and lat/loncoordinates is provided.

The PLA file 110 is a file which for each district correlates each PLAwhich is unique to and has been reserved for use in the district withits corresponding grid address.

The navigational system described above may be mounted in a vehicle orcontained in a portable device, for example. Additionally, thenavigational system may stand alone or may be integrated into existingdevices, such as portable phones. Further, the subject invention may beincorporated into a general computational device such as amicroprocessor. Since the physical manifestation of the navigationalsystem is so flexible, there are numerous foreseeable applications.

DETAILS AND EXAMPLES OF SYSTEM IMPLEMENTATION

The examples set forth below describe various details of variousimplementations of the system. Examples 1, 2, and 3 demonstrate specificimplementations of one embodiment of the invention: Example 1demonstrates the use of Hierarchial Identifiers for districts which arecorrelated with Country, State/Province, and City districts along withPLA's and a purely numeric ULA grid referencing system based upon adistrict grid size of approximately 185 kilometers north to southExample 2 demonstrates the use of the Hierarchial Identifiers describedin Example 1 along with an alternating alpha-numeric ULA gridreferencing system Example 3 demonstrates the use of a smaller City Gridand the resulting higher precision at various grid levels.

EXAMPLE 1 Hierarchical Identifiers For Country, State/Province, City

The example assumes the existence of higher levels of hierarchical codesfor identifying countries, states/provinces, and cities. The top levelcodes can be used, implied by context, or specifically ignored by theuse of dots (periods) to make it clear how many codes have been omitted.A code of `US.CA.LA` might be represented as `LA`, `..LA`, or by`CA.LA`, depending on the geogrrphic context or the need for clarity.

In all cases, upper level codes are dropped when the geographic contextis clear, to prefix with dots (periods) when necessary to insureclarity, and to append lower levels to add precision.

Country Codes

Top level: two alpha character mnemonic (possibly based on Internetdomain codes).

Examples:

United States=US

Australia=AU

Canada=CA

State/Province Codes

Second level: two character mnemonics (advantageously based on U.S.postal codes within the U.S.).

Examples:

California=CA

New York=NY

City Codes

Third level: two or three alpha character mnemonics from city nameunique within each state.

Examples:

Carbondale=CAR

Hartford=HAR

Los Angeles=LA

New York City=NYC

Proprietay Codes

Fourth level; one or more alpha or numeric characters which are uniquewithin a specific grid or map with a unique map code.

Examples:

MACD, DISNEY, EXXON, etc.

An example of a use of a PLA might be US.GA.ALB.MACD to refer to aMacDonalds in Albany, Ga.; US.GA.ALB.MACD* to refer to the closest(s)one in Albany, Ga.; or MACD* to refer to the closest(s) ones in anycity.

The code ..ALB.MACD* could refer to either the nearest MacDonalds inAlbany, Ga. or Albany N.Y. and context. .NY.ALB.MACD* would resolve thecontext.

City Grid

This optional code is at a fourth or fifth level; identified by thefirst use of a pair of numeric characters in the city grid code. Thecity grid system requires an approximate city centroid described in alocational reference system such as geodetic latitude and longitude andthe meaning of each pair of grid designators. The city grid origin isdefined at the south-west coordinate system intersection valuecorresponding to exact values of the largest grid resolution precisionthat is defined in the city grid. placing the district centroid withinthe center grid cell of the system.

In the nominal city grid system, the grid cells are orthogonal to thedefining coordinate system; however, rotations and scale parameters canbe used to re-define the relationship between the city grid and thereference frame. False easting and false northing offsets (translations)are normally used to avoid negative numbering or to allow convenientordering of alphanumeric designators.

Conversion from the defining reference frame (e.g., lat/lon) to citygrid designators (i.e., ULAs) is accomplished by computing conversionconstants based on the initial reference frame and the specific citygrid definitions. When geographic context has already been established,grid designators are computed with respect to the currently selecteddistrict. When no district has been selected as the preferred one, thenearest district centroid is used as the basis for the grid designators.Conversion from city grid to coordinates in the defining system isaccomplished by applying translation (and when applicable rotation andscale) parameters to the succession of grid designators until theprecision implied by the number of grid cell designator pairs isreached.

The city grid is nominally based on a locational reference system thatcan be tied to other reference systems. In the nominal system, theunderlying locational reference system datum is the World GeodeticSystem 1984 (WGS-84). Geodetic coordinates with respect to this datumcan be converted to coordinates in a large number of other referencesystems, allowing the city grid designators to be used with respect toother systems and other geodetic datums allowing conversion to UniversalTransverse Mercator (UTM) systems, State Plane Systems, National GridSystems, other horizontal coordinate system, or map projection.

The city grid origin is defined at the ten minute of latitude and tenminute of longitude intersection nearest the city centroid. This placesthe origin within five minutes of latitude and longitude of the citycentroid. The radial distance of the city grid origin is then alwayswithin about 10 km of the nominal city center.

Each Arid is then defined based on this origin by placing a gridcentered at the origin with a false easting and northing=halfway betweenminimum and maximum numeric characters. Grid cells are identified by aneasting cell designator paired with a northing cell designator withsuccessive pairs of designators defining grid cells of increasingprecision.

Highest level; least precision two numeric characteristics, East isalways first, North is always second, minirnurn is always 0 and maximumis always 9.

The false easting puts the division between 4 and 5 at the grid originnorth and east. Each highest level grid consists of a ten by ten region(100 grid rectangles).

Next lower level; higher precision, divides each numeric grid into a tenby ten grid (100 grid rectangles) area. East is always first, north isalways second. Minmum is always 0 and maximum is always 9.

The false easting again puts the grid rectangle center at the divisionbetween 4 and 5.

Next lower levels repeat the numeric code above dividing each highergrid rectangle into a ten by ten rectangle area.

If each city grid origin is at an integer intersection of an even tenminutes of latitude and longitude, the first level numeric gridrectangles each cover an area of approximately 100 square nauticalmiles, or about 343 square kilometers with grid cells whose north-southextent is about 18.5 kilometers. Thus the entire set of first level gridcells covers a distance of about 185 kilometers from north to south anda shorter distance from west to east, depending on latitude.

Each second level city grid cell is 1/10^(th) of the next higher levelgrid cell, or 1 minute of latitude and longitude, about 1850 metersnorth to south.

Each third level city grid cell is then 1/10^(th) of the second levelgrid, or 6 seconds of latitude and longitude, about 185 meters north tosouth.

Each fourth level city grid cell is then 1/10^(th) of the third levelgrid, about 18.5 meters north to south, around 340 square meters.

Since this fourth level grid corresponds to a resolution some five timesmore precise than un-aided GPS accuracy (with Selective Availability), afifth level grid may not be required. Following the same 1/10^(th) ruleas the higher level grids, a fifth grid cell would measure 1.85 meterson a side, well within the accuracy of differentiailv-aided GPS.

Cities close to each other can each employ their own city grid even whenthey overlap. When questions of which city grid occur the city code (orall the higher level codes) can be attached to remove ambiguity.

An example of a use of a ULA might be US.GA.ALB.13 to refer to an areaabout 20 kilometers wide southwest of the center of Albany, Ga. Then.ALB.13.78 would refer to an area about 2 kilometers wide near thenortheast corner of the previous example. So would .13.78 if thegeographic context was established as Albany, Ga.

The code .US.GA.ALB.13.78.27.14 would refer to the smallest unit ofabout 9 meters within an explicitly defined place. .78.27.14 would referto the same place in context.

EXAMPLE 2

In addition to the example above which demonstrates the logic andstructure of the XYZ.12.34.56.78 format, this example describes the useof a grid format and ULA utilizing the XYZ.12.aa.34.aa format. TheCountry, State/Province, City and Proprietary Codes remain as describedin the previous example, but the optional City Grid is structureddifferently. The grid code is still initially identified by a pair ofnumeric characters, and the city grid origin is defined at the tenminute of latitude and ten minute of longitude intersection nearest thecity centroid as in the previous example. The definition of each gridand the false casting and northing, as well as the structure of theFirst grid level, is also as described in the preceding example.

The next lower level of the grid divides each numeric grid into a twentyby twenty grid (400 grid rectangles) area. East is always first, northis always second. The minimum is A from a character set consisting ofABCDEFGHJKLMNPQRSTUV, and the maximum is V. The false easting puts thegrid rectangle center at the division between K and L.

The next lower level repeats the numeric code as described in thepreceding example dividing each higher grid rectangle into a ten by tenrectangle area and the next lower level repeats the alpha code describedabove in this example dividing each higher grid rectangle into a twentyby twenty rectangle area

If the city grid is the same size as the preceding example, each secondlevel city grid square (represented by the code XYZ.12.aa) is 1/20^(th)of the first numeric grid square, 30 seconds of latitude and longitude,or about 920 meters north to south. The third level city grid square(represented by the code XYZ.12.aa.23) would result in a grid rectanglesize of approximately 3 seconds of latitude and longitude, or about 92meters north to south. The fourth level city grid square (represented bythe code XYZ.12.aa.23.aa) would be 1/20^(th) of the previous city gridsquare size, resulting in a grid rectangle size of approximately 0.15seconds of latitude and longitude, or about 5 meters north to south.

It should be appreciated that it is possible to define embodinents inwhich these higher level portions are defined in terms of either numericor alpha characters, or alternatively, in terms of mixed alpha andnumeric characters.

EXAMPLE 3

This example demonstrates the different precision achievable by varyingthe size of the city grid of a particular district. This example uses asample city grid designator "US.TX.AUS.45.45.77.45," with a districtcentroid of 30 degrees, 17 minutes north latitude and 97 degrees, 45minutes of west longitude for an Austin, Tex., city grid district with adistrict designator, "US.TX.AUS." For a city grid easting and northingresolution of 1 minute of latitude and longitude for the largestresolution grid designator pair, the grid origin would be placed at 30degrees, 17 minutes north latitude and 97 degrees, 45 minutes westlongitude.

For numeric city grid designators with no rotation or scale, and with afalse easting and northing of five grid cells, the designator"US.TX.AUS.45.45.77.45" would correspond to a geodetic position of 30degrees, 15 minute, 45.0 seconds north latitude, and 97 degrees, 45minutes, 15.0 seconds west longitude. The precision of the smallest gridcell would be one thousandth of a minute of latitude and longitudecorresponding to approximately 1.6 meters of easting and 1.9 meters ofnorthing. By reducing the number of designator pairs the precision ofthe implied geodetic position is also reduced. In this example, adesignator of ".TX.AUS.45.45", would refer to an area one tenth of oneminute of latitude by one minute of longitude in area or approximately185 meters north to south, ".AUS.45.45.77" would refer to an areaone-hundredth of one minute by one-hundredth of one minute, orapproximately 18.5 meters north to south.

EXAMPLES OF USE

Set forth below are several examples of how the invention can be used.

Examples 4 through 7 reflect situations in which the invention may beused and provide marked improvements in function and utility overtraditional lat/lon based systems. Example 8 demonstrates certainaspects of the invention related to a particular geographic area and twomaps of partially overlapping areas.

EXAMPLE 4

The subject invention may be used for general vehicular navigation, todrive from Los Angeles to the visitor's center at the Grand Canyon. Thedriver must first determine the address for the target location, andthen input the address into the navigational system. There are severalalternatives for locating the PLA or ULA. For example, the driver mayread travel brochures that the ULA/PLA addresses; the driver may alsoreview a map which contains ULA/PLA annotations; or the driver couldjust call the Visitor's Center and ask them for their PLA or ULA.Alternatively, the driver, using the input device, could search the PLAdatabase to find if the Grand Canyon visitor's center has a PLA. Oncethe address is determined, the driver enters the PLA or ULA address intoa navigational system, and the navigational system will direct thedriver to the proper destination.

EXAMPLE 5

Second, the subject invention may be used to direct local traffic to aparticular point of interest For example, if the driver above istraveling along a highway and becomes hungry and desires to eat at aparticular fast-food chain, the driver could interrogate the system datato find any nearby chain restaurants. The driver simply queries thesystem for occurrences of the fast-food chain's PLA, and, since thesystem is aware of its current location, the chain's restaurants may belisted by proximity. The driver simply selects one of the restaurants,and the navigational system directs the driver to that location.Additionally, a local restaurant may advertise a ULA or PLA for itslocation, so a driver, seeing a billboard or advertisement containing aULA or PLA address, could input that address and be directed to therestaurant location. Because of the unique style of the addresses andfeatures of the subject invention, these addresses are particularly easyto input with a minimum chance of error, decreasing the risk ofaccidents and increasing the likelihood of going to the desiredlocation.

EXAMPLE 6

Third, the subject invention is particularly well suited forcustomization by individual or team users, facilitating intra-groupcommunication and navigation. For example, if a group of hikers desiresto split up and explore a particular area, they each could set theirportable navigation devices to reference a custom grid with anappropriate grid size and location for the explorable area that allowssufficient resolution with a minimum number of digits or characters.Now, as the hikers communicate with each other or record interestinglocational information, the data may be easily and accurately used andreferenced to a meaningful location. This ability to set a user-definedreference point and grid size would also be useful for rescue teamsperforming search and rescue operations by allowing the search andrescue team to instantly establish a arid size and location for anysearch.

EXAMPLE 7

Fourth, the subject invention has emergency utility. For example, if ahiker above needs emergency assistance, the navigational system canprovide a locational ULA that is easy to read and communicate by voiceor numeric only key pad, which reduces both the ambiguity, risk and timeinvolved in describing an emergency location. Alternatively, this ULAmay be automatically communicated to emergency personnel if thenavigational system integrates with a portable phone, two way pager, orother portable communication device.

EXAMPLE 8

An example illustrating the use of PLAs and ULAs in a specificgeographical context, Yosemite National Park, will now be described.FIG. 6 illustrates a paper map with an assigned name of CA.YSB(indicated by identifying numeral 111). Within the boundariesrepresented on this map, the following PLAs have been reserved:

    ______________________________________                                                  Description   Corresponding FIG. 6                                    PLA of Location identifying numeral                                         ______________________________________                                        HFDM      Half Dome     115                                                     1 Ahwahnee Hotel 112                                                          GCRP Glacier Point 114                                                        YSMF Lower Yosemite Fall 113                                                ______________________________________                                    

FIG. 7 illustrates a district with an assigned name of CA.YSM (indicatedby identifying numeral 120). Within this district, the following PLAshave been reserved:

    ______________________________________                                                 Description      Corresponding FIG. 7                                  PLA of Location identifying numeral                                         ______________________________________                                        HCHY     Hetch Hetchy     121                                                   11 White Wolf 122                                                             NENT Big Oak Flat Entrance 123                                                GCRP Glacier Point 126                                                        WENT Arch Rock Entrance 124                                                   BDGP Badger Pass 125                                                          1 Wawona Information Center 128                                               SENT South Entrance 127                                                     ______________________________________                                    

The following points should be noted from this example:

First, the name CA.YSB is for the specific map included in FIG. 6, andnot for a district in which all of the area contained on the map isincluded. This feature allows assignment of specific PLA's for specificmaps without regard to the district, thereby providing clarity insituations where the area covered by the map overlaps one or moredistricts.

Second, the name CA.YSM is the name of the district in which the areaincluded in the map in FIG. 7 is located, thereby allowing areasincluded within this map to be referenced by either PLAs (e.g.CA.YSM.HCHY) or ULAs (e.g. CA.YSM.32.84.23.43) without the need tore-identify the name of the district or map.

Third, the areas covered by the CA.YSM district and the CA.YSB mapoverlap, allowing PLA references to either the YSM district or the YSBmap. (Note also that the system might also define YSB as a districtwhich could be utilized in determining ULA's with reference to the YSBdistrict, in which case the YSB and YSM districts would also partiallyoverlap.)

Fourth, the PLA's for particular locations may either be identicalexcept for the district name (e.g. GCRP in FIG. 6 and GCRP in FIG. 7refer to the same location) or identical PLA's may apply to differentlocations in different districts or on different maps (e.g. "1" in FIG.6 and "1" in FIG. 7 refer to different locations on each of therespective maps). This is consistent with the principle that a PLA needonly be unique within the district in which it is defined.

All of the features described in this example are designed to allow aninitial manual or electronic input (either a district code, cell code,or specific map code) which allows users to use PLA's or ULA'sidentified on a specific map with a minimum number of keystrokes,thereby minimizing data entry, confusion, and ambiguity.

EXAMPLES OF SOFTWARE IMPLEMENTATION

Examples 9, 10, and 11 demonstrate certain characteristics of files,pseudo-codes, and program screens of particular embodiments of theinvention. (Note that the data contained in the files is provided forillustrative purposes only).

EXAMPLE 9

In this example, formats of specific files that are used in oneimplementation of the subject invention are described. Four files aredescribed: GO2CITY.DAT, STATES.DAT,PROPGO2.DAT, and COUNTRYS.DAT.

The GO2CITY2.DAT file, illustrated in FIGS. 8a-8b, defines the referencepoints for a plurality of pre-defined districts centered around specificcities. For each reference point, there is provided the name of thedistrict, the name of the reference point, and the global coordinates ofthe reference point Thus, the first entry of this file "AK, AiNC,Anchorage, 149W54,61N13," indicates that there is a district in thestate of Alaska. centered around Anchorage, with the reference pointthereof having the following global coordinates: 149W54,61N13.

The STATES.DAT file, illustrated in FIG. 9, simply defines the mnemonicsused in GO2CITY2.DAT to define states.

The PROPGO2.DAT file, illustrated in FIGS. 10a-10c, defines theproprietary names which have been reserved for each district This filecorrelates each such proprietary name with the global coordinatesassociated with that name. Thus, the first entry of this file,"US.CA.NWB.MAC2, 117W52.360, 33N39.549" indicates that, in a districtcentered around Newport Beach, Calif., there is a MacDonalds having thefollowing global lat/lon coordinates address: 117W52.360, 33N39.549.

The COUNTRYS.DAT file, illustrated in FIG. 11, simply defines thecountry mnemonics used in PROPGO2.DAT.

EXAMPLE 10

This example illustrates screen formats as displayed on an output devicein an implementation of the subject invention. FIG. 12a is a screenillustrating the input of a ULA or grid address into a navigationalsystem, with the system determining and outputting correspondinglatitude and longitude coordinates. FIG. 12b illustrates the input of aPLA, with the system determining and outputting corresponding latitudeand longitude coordinates. FIG. 12c illustrates the capability of thesystem to interpret the context, i.e. district address, of previousaddresses, and to assume that the same distinct addresses applies tosubsequent specific addresses until notified otherwise. In this specificexample, the proprietary name MAC2 was input with the system assumingthat the district name associated with the previous example relating toMAC1, i.e., the CA.NWB, district name, applied to this example as well.Thus, in FIG. 12c, only the identifier "MAC2" need be input to thesystem, it being assumed that the district identifier "CA.NWB" appliesto this request as well.

EXAMPLE 11

This document is a functional description of a computer program,Go2Grid, which embodies one or more aspects of the subject invention.The program is written in the "C++" programming language and its purposeis to demonstrate the feasibility of conversion between city grid andproprietary codes and geodetic coordinates.

Program flow is described using a series of pseudo-code statements. Thefunctions required to perform these tasks are described. The datavariable types and structures are defined. The parameters required forimplementation of two possible city grid designators are defined.

Program Flow

    ______________________________________                                        Set all defined parameters to their default values                              Northern latitudes are positive                                               Eastern longitudes are negative                                               The assumed geodetic datum is World Geodetic System 1984 (WGS-84)            The last geodetic position is used to initialize the City Grid designator     The user screen is initialized                                                Monitor keystrokes or navigation receiver input                               For any City Grid designator change                                           Parse user input                                                              If change in City Code                                                        Compute city position from designator                                         Fill City Code                                                                Fill Country and State Codes                                                  If change in State Code                                                       Fill Country and State Codes                                                  If change in Country Code                                                     Fill Country Code                                                             If change in entire City Grid Designator                                      If a Universal Go2 Code                                                       Fill Country, State, City and Grid Codes                                      If a Proprietary Go2 Code                                                     Fill Proprietary Code                                                         Compute geodetic coordinates for this Go2 Designator                          For any change in geodetic coordinates                                        Parse user input                                                              If user has requested a Universal Code                                        If current geographic context is changed                                      Get Go2 Codes from latitude and longitude                                     Find closest city                                                             Set new City Grid center                                                      Fill Country, State, City codes                                               Compute City Grid Codes for each level of precision                           Reset User Screen display                                                     Continue                                                                     ______________________________________                                    

Function

The following functions are used by the Go2Grid sample program anembodiment of the city grid concept:

    ______________________________________                                        getdeg                                                                   extracts decimal degrees from character strings                         grange computes geodetic range between two positions                    dmsdeg extracts degrees, minutes, seconds from                  decimal degrees                                                         degdms forms decimal degrees from degrees, minutes,                    seconds                                                                 getcenter computes geodetic coordinates of City Grid                   center from city                                                         centroid                                                                     getgrid computes City Grid codes for level of precision                 getkeys parses user keyboard input                        parsego2 parses Go2 City Grid designator                         addlatlon concatenates next level of precision onto                    geodetic                                                                 coordinates                                                                  getnextcity finds next city in current state/province list       getprevcity find previous city in current state/province               list                                                                    getcost fills Go2 City Grid designator with country and                state/                                                                   province codes                                                               putscreen fills display with current city Grid designator              and geodetic                                                             coordinates                                                                  getnextstate finds next state/province in current country              list                                                                    getprevstate find previous state/province in current                   country list                                                          ______________________________________                                    

Types and Structures

The Go2Grid embodiment sample program defines the following variablestructures in addition to the usual character, integer, float, anddouble types:

    ______________________________________                                                 typedef struct ccstruct {                                              char city.sub.-- code[4];                                                     char city[60];                                                                char state.sub.-- code[3];                                                    char state[60];                                                               char country.sub.-- code[3];                                                  char country[60];                                                             char longitude[32];                                                           char latitude[32];                                                            double lat;                                                                   double lon;                                                                   double centerlat;                                                             double centerion;                                                             };                                                                            typedef struct latlonstruct {                                                 int latdeg;                                                                   int latmin;                                                                   int latsec;                                                                   int londeg;                                                                   int lonmin;                                                                   int lonsec;                                                                   };                                                                          ______________________________________                                    

Program Definitions

The following definitions are used within the Go2Grid sample program:

    ______________________________________                                        /* grid types */                                                                /* a gridtype ═ 1 is numeric with 10 minutes, 1.0, 0.1, and 0.001       grids */                                                                        /* a gridtype ═ 2 is alphanumeric with 10, 0.5, 0.05 and 0.0025         grids */                                                                        #define GRIDTYPE 1                                                            #define TITLE "Go2 and Geographic Coordinate Converter"                       #define VERSION "(4/3/96)"                                                    /* lines */                                                                   #define TITLELINE 1                                                           #define GO2CONTEXTLINE 5                                                      #define GEOCONTEXTLINE 10                                                     #define HELPLINE 15                                                           #define MESSAGELINE 18                                                        #define COUNTRYLINE 20                                                        #deflne STATELINE 21                                                          #define CITYLINE 22                                                           #define GO2LINE 23                                                            #deflne LATLINE 24                                                            #define LONLINE 25                                                            #define INCOL 23                                                              #define OUTCOL 5                                                              #if GRID TYPE═1                                                           /* GRIDGRAIN*/                                                                #define GRDKIND "Numeric City Grid"                                           #define GRDDEF "Grid Precision: Level 1=1.0'; Level 2=1.0';                   Level 3=0.1'; Level 4=0.01'"                                                  #define GRIDCHARS "Designators Levels 1, 2, 3 and 4:                          [01232456789]"                                                                #define LEVEL 1.sub.-- EGRAIN 10.0                                            #define LEVEL 1.sub.-- NGRAIN 10.0                                            #define LEVEL 1.sub.-- ECHARS "0123456789"                                    #define LEVEL 1.sub.-- NCHARS "0123456789"                                    #define LEVEL 1.sub.-- EGRIDS 10                                              #define LEVEL 1.sub.-- NGRIDS 10                                              #define LEVEL 2.sub.-- EGRAIN 1.0                                             #define LEVEL 2.sub.-- NGRAIN 1.0                                             #define LEVEL 2.sub.-- ECHARS "0123456789"                                    #define LEVEL 2.sub.-- NCHARS "0123456789"                                    #define LEVEL 2.sub.-- EGRIDS 1.0                                             #define LEVEL 2.sub.-- NGRDS 1.0                                              #define LEVEL 3.sub.-- EGRAIN 1.0                                             #define LEVEL 3.sub.-- NGRAIN 0.10                                            #define LEVEL 3.sub.-- ECHARS "0123456789"                                    #define LEVEL 3.sub.-- NCHARS "0123456789"                                    #define LEVEL 3.sub.-- EGRIDS 10                                              #define LEVEL 3.sub.-- NGRIDS 10                                              #define LEVEL 4.sub.-- EGRAIN 0.010                                           #define LEVEL 4.sub.-- NGRAIN 0.010                                           #define LEVEL 4.sub.-- ECHARS "0123456789"                                    #define LEVEL 4.sub.-- NCHARS "0123456789"                                    #define LEVEL 4.sub.-- EGRIDS 10                                              #define LEVEL 4.sub.-- NGRIDS 10                                              #else if GRIDTYPE═2                                                       #define GRIDKIND "AlphaNumeric City Grid"                                     #define GRIDDEF "Grid Precision: Level 1=10'; Level 2=0.5';                   Level 3=0.05'; Level 4=0.0025'"                                               #define GRIDCHARS Designators Levels 1&3:[01232456789];                       Levels 2&4:[ABCDEFGHJKLMNPRSTUVW]"                                            /* GRID GRAIN */                                                              #define LEVEL 1.sub.-- EGRAIN 10.0                                            #define LEVEL 1.sub.-- NGRAIN 10.0                                            #define LEVEL 1.sub.-- ECHARS "0123456789"                                    #define LEVEL 1.sub.-- NCHARS "0123456789"                                    #define LEVEL 1.sub.-- EGRIDS 10                                              #define LEVEL 1.sub.-- NGRIDS 10                                              #define LEVEL 2.sub.-- EGRAIN 0.5                                             #define LEVEL 2.sub.-- NGRAIN 0.5                                             #define LEVEL 2.sub.-- ECHARS "ABCDEFGHJKLMNPRSTUVW"                          #define LEVEL 2.sub.-- NCHARS "ABCDEFGHJKLMNPRSTUVW"                          #define LEVEL 2.sub.-- EGRIDS 20                                              #define LEVEL 2.sub.-- NGRIDS 20                                              #define LEVEL 3.sub.-- EGRAIN 0.05                                            #define LEVEL 3.sub.-- NGRAIN 0.05                                            #define LEVEL 3.sub.-- ECHARS "0123456789"                                    #define LEVEL 3.sub.-- NCHARS "0123456789"                                    #define LEVEL 3.sub.-- EGR.spsp.10                                            #define LEVEL 3.sub.-- NGR.spsp.10                                            #define LEVEL 4.sub.-- EGRAIN 0.0025                                          #define LEVEL 4.sub.-- NGRAIN 0.0025                                          #define LEVEL 4.sub.-- ECHARS "ABCDEFGHJKLMNPRSTUVW"                          #define LEVEL 4.sub.-- NCHARS "ABCDEFGHJKLMNPRSTUVW"                          #define LEVEL 4.sub.-- EGRIDS 20                                              #define LEVEL 4.sub.-- NGRIDS 20                                              #endif                                                                      ______________________________________                                    

While embodiments and applications of this invention have been shown anddescribed, it would be apparent to those in the field that many moremodifications are possible without departing from the inventive conceptsherein The invention, therefore, is not to be restricted except in thespirit of the appended claims.

What is claimed is:
 1. A method for defining and using an improvedlocational referencing system comprising the steps of:defining aplurality of arbitrarily-shaped districts, each associated with aparticular location having a unique district name, and each associatedwith a reference point defined in terms of a well-known geographicreferencing system; sub-dividing each of said districts into a pluralityof cells having an arbitrary orientation and scale, wherein each of saidcells is identified by a first unique cell number in accordance to itsrelative position within the associated district; and saving saidreference point, said unique district name, and factors associated withsaid arbitrary orientation and scale for each of said districts.
 2. Themethod of claim 1, further comprising the steps of:selecting a firstselected location by identifying one of said cells within one of saiddistricts; and creating a first universal location address (ULA) byappending said unique cell number to said unique district nameassociated with said first selected location.
 3. The method of claim 2,further comprising the step of:converting said first ULA to thewell-known geographical referencing system by mathematically applyingsaid unique cell number to said reference point corresponding to saidassociated unique district name in accordance with the arbitraryorientation and scale factors from said saving step.
 4. The method ofclaim 2, further comprising the steps of:dividing at least one of saidcells into a plurality of smaller cells, each having a predefined size,wherein each of said smaller cells is identified by a second unique cellnumber in accordance to its relative position within said at least oneof said cells; and storing said predefined size of said smaller cells.5. The method of claim 4, further comprising the steps of:selecting asecond particular address by identifying one of said smaller cells; andcreating a second ULA by appending said second unique cell number ofsaid one of said smaller cells to said first ULA.
 6. The method of claim4, wherein said dividing and storing steps are repeated until a desiredaddress resolution is achieved.
 7. The method of claim 4, furthercomprising the steps of:selecting a second selected location byidentifying one of said smaller cells; creating a second ULA byappending each of said second unique cell numbers associated with saidsecond selected location to said first ULA in an order corresponding tothe second selected cell's hierarchy.
 8. Navigational apparatuscomprising:a GPS receiver by means of which global coordinates of afirst selected location within a geographical area can be provided; aninput device by means of which a locational address of a second selectedlocation within the geographical area can be provided, the locationaladdress comprising a specific locational address appended to generalposition information; a storage device in which data descriptive of aplurality of pre-defined grids is stored, each of the gridscorresponding to a geographical area and havinga plurality of cells; areference location; global coordinates of the reference location; and atleast one parameter defining cell size and orientation; a processorcoupled to the GPS receiver, the input device and the storage device,said processor being configured such thatat least one of the pluralityof grids is selectable based on the general position information; theglobal coordinates of the second selected location are determinablebased on the data descriptive of the selected grid and the specificlocational address; and an indicator which is determinable by comparingthe global coordinates of the first selected location with the globalcoordinates of the second selected location; and an output devicecoupled to the processor, wherein the indicator can be output by meansof the output device.
 9. Apparatus according to claim 8, wherein thespecific locational address consists of a plurality of hierarchicalcodes.
 10. Apparatus according claim 9, wherein each grid cell issubdivided into a plurality of sub-cells.
 11. Apparatus according toclaim 8, wherein the specific locational address is a proprietaryname,locational information of the second selected location associatedwith the proprietary name is stored in the storage device, and theglobal coordinates of the second selected location are determinablefurther based on the locational information.
 12. Apparatus accordingclaim 11, wherein each grid cell is subdivided into a plurality ofsub-cells.
 13. Apparatus according claim 8, wherein each grid cell issubdivided into a plurality of sub-cells.
 14. Apparatus according to anyof the claims 13 to 12, whereina specific locational address of a thirdselected location within the geographical area can be provided by meansof the input device; the processor is further configured such thattheglobal coordinates of the third selected location are determinable basedon the data descriptive of the selected grid and the specific locationaladdress of the third selected location; and a second indicator which isdeterminable by comparing the global coordinates of the first selectedlocation with the global coordinates of the third selected location and;the second indicator can be output by means of the output device. 15.Apparatus according to claim 14, wherein the global coordinates arelatitude and longitude coordinates.
 16. Apparatus according claim 15,wherein a specific location address is acceptable by means of the inputdevice, and said processor being further configured such that a completelocational address can be created by combining the known generalposition information with the specific locational address.
 17. Apparatusaccording to claim 14 wherein the second indicator is selected from thegroup comprising a distance indicator, a direction indicator, and adistance and direction indicator.
 18. Apparatus according to claim 8wherein the indicator is selected from the group comprising a distanceindicator, a direction indicator, and a distance and directionindicator.
 19. A method of indicating a direction towards a desiredlocation comprising the following steps:providing global coordinates ofa first selected location within a geographical area; providing alocational address of a second selected location within the geographicalarea, the locational address comprising a specific locational addressappended to general position information; storing data descriptive of aplurality of pre-defined grids, each of the grids corresponding to ageographical area and havinga plurality of cells; a reference location;global coordinates of the reference location; and at least one parameterdefining cell size and orientation; selecting one of the plurality ofgrids based on the general position information; determining the globalcoordinates of the second selected location based on the datadescriptive of the selected grid and the specific locational address;determining an indicator by comparing the global coordinates of thefirst selected location with that of the second selected location; andoutputting the indicator.
 20. The method according to claim 19, whereinthe specific locational address consists of a plurality of hierarchicalcodes.
 21. The method according to claim 20, wherein each grid cell issubdivided into a plurality of sub-cells.
 22. The method according toclaim 19, whereinthe specific locational address is a proprietary name,the method further comprises the step of storing locational informationof the second selected location associated with the proprietary name,and wherein the step of determining the global coordinates of the secondselected location is further based on the locational information. 23.The method according to claim 22, wherein each grid cell is subdividedinto a plurality of sub-cells.
 24. The method according to claim 19,wherein each grid cell is subdivided into a plurality of sub-cells. 25.The method according to any of the claims 24 to 23, further comprisingthe steps ofproviding a specific locational address of a third selectedlocation within the geographical area; determining the globalcoordinates of the third selected location based on the data descriptiveof the selected grid and the specific location address of the thirdselected location; determining a second indicator by comparing theglobal coordinates of the first selected location with the globalcoordinates of the third selected location; and outputting the secondindicator.
 26. The method according to claim 25, wherein the globalcoordinates are latitude and longitude coordinates.
 27. The methodaccording to claim 26, further comprising the steps of accepting aspecific locational address, and creating a complete locational addressby combining the known general position information with the specificlocational address.
 28. The method of claim 25 wherein the secondindicator is selected from the group comprising a distance indicator, adirection indicator, and a distance and direction indicator.
 29. Themethod of claim 19 wherein the indicator is selected from the groupcomprising a distance indicator, a direction indicator, and a distanceand direction indicator.